There are many questions about the Code (CfSH). Below are the most common.

Is it mandatory?

In some planning authorities a code level 3 commitment is required as part of the planning applications.
I others, it is desirable and the rest there is no specific requirement

Note though, all new build houses must have a Code rating, but a builder can obtain a Code 0 rating by complying with building regulations. This can be downloaded from the government web site.

What are the Code ratings?

Their are Code ratings 0 through to 6. Level 0 is current building regulations. Level 3 is the most common currently and represents 25% reduction in SAP calculations, reductions in water usage and seven other areas of concern.
Level 5 is a carbon neutral home and Level 6 is putting some energy back into the world.

When do I need to start working on getting a Code rating?

The Code assessment process starts at the design stage of your project. There are many consideration that MUST be taken in to the design, so engage an assessor very early on in the process and get to grips with all it's requirements.

Will it cost me more to attain the various Code Levels?

Yes, it will, but you should also save in the long run with lower running costs. Of course if you are building to sell on, these lower running costs will help in selling the house.